Seattle, WA Development Impact Fees (2026)
Normalized development impact fees, water & sewer connection (tap/SDC) fees, and mitigation fees for Seattle, Washington — per dwelling unit, by category, with links to every official source.
What a single-family home pays in Seattle
$9,500 total per unit across 2 fee categories.
- Water connection (tap / SDC)$6,900
- Sewer connection (tap / SDC)$2,600
At $9,500, Seattle is below the Washington tracked median of $13,063 — relatively affordable to build in.
Full fee schedule — single-family
Impact / development fees
| Fee (local term) | Basis | Amount | Source · effective |
|---|---|---|---|
Drainage / stormwater Drainage System Development Charge (SDC) — NEW SPU Drainage SDC effective 1/1/2026, charged per 1,000 sq ft of NEW hard (impervious) surface when hard surface increases. Only applicable within the City of Seattle. Excluded from the per-dwelling-unit total because it depends on the amount of new impervious area, not a flat per-unit charge. alternative · not added to total | per 1,000 sq ft | $1,225 | Seattle Public Utilities (City of Seattle) Jan 1, 2026High |
Water & sewer connection fees
| Fee (local term) | Basis | Amount | Source · effective |
|---|---|---|---|
Water connection (tap / SDC) Water System Development Charge (SDC) — 3/4-inch meter — SPU Water SDC for a standard residential 3/4-inch (0.75") meter, the typical single-family service size, effective 1/1/2026. SDC = SDC Unit Rate x SDC Customer Equivalent (SDCE 1.0 for 3/4" meter). Additive with the Wastewater SDC. Credit given for existing water service. | per meter | $6,900 | Seattle Public Utilities (City of Seattle) Jan 1, 2026High |
Sewer connection (tap / SDC) Wastewater System Development Charge (SDC) — 3/4-inch meter — NEW SPU Wastewater SDC effective 1/1/2026 for a standard residential 3/4-inch (0.75") meter. Only charged inside the City of Seattle. Not charged for irrigation or fire services. Additive with the Water SDC (combined water+wastewater = $9,500 for a 3/4" meter). | per meter | $2,600 | Seattle Public Utilities (City of Seattle) Jan 1, 2026High |
Sewer connection (tap / SDC) King County Wastewater Treatment Capacity Charge (regional, separate district) — SEPARATE DISTRICT: levied by King County Wastewater Treatment Division (not the City of Seattle), but a new connection inside Seattle pays it because Seattle's sewage is treated by King County's regional system. $77.99 per RCE PER MONTH (a medium 1,500-2,999 sq ft single-family home = 1.0 RCE = $77.99/mo; small <1,500 sf = 0.81 RCE; large 3,000+ sf = 1.16 RCE), billed quarterly over 15 years for connections on/after 1/1/2026. A discounted lump-sum payoff is available but the dollar amount is not published by King County. unitBasis 'other' = per RCE per month; excluded from one-time per-unit total because it is a recurring 15-year charge, not a one-time connection fee. alternative · not added to total | $77.99 | King County Department of Natural Resources and Parks (DNRP) Jan 1, 2026High | |
Water connection (tap / SDC) Water + Wastewater SDC — 1-inch meter (larger service variant) — Alternative meter-size variant (1-inch meter): Water SDC $11,730 + Wastewater SDC $4,420 = $16,150 total. Excluded from total — the 3/4-inch meter is the representative single-family service. Listed to show how SDCs scale by meter size. alternative · not added to total | per meter | $16,150 | Seattle Public Utilities (City of Seattle) Jan 1, 2026High |
Coverage & caveats
SEATTLE DOES NOT CHARGE IMPACT FEES. The City of Seattle has not adopted any RCW 82.02 impact fees, so there are NO transportation/road, parks, fire, police, library, or open-space impact fees, and NO school impact fee. (Seattle Public Schools does not levy a school impact fee within city limits; the King County school-impact-fee program applies only to unincorporated King County and other cities, not Seattle.) A transportation impact fee has been studied/proposed since ~2015 but as of mid-2026 remains unadopted and tied up in SEPA litigation. Confirmed by MRSC Impact Fees topic page and Seattle OPCD "Impact Fees" page. INSTEAD OF IMPACT FEES, Seattle uses the Mandatory Housing Affordability (MHA) program (SMC 23.58C / MHA-R for residential) — an affordable-housing developer contribution. MHA is NOT a flat per-dwelling-unit fee and is NOT included as a per-unit row here because: (1) it applies ONLY to property that has been rezoned with an MHA suffix (M)/(M1)/(M2) (or certain zones where MHA is effective), not to ordinary single-family lots; and (2) the payment is calculated on total gross residential floor area times a per-square-foot "payment calculation amount" that varies by MHA area (low/medium/high) and is CPI-adjusted every March 1. SDCI Tip #257 (updated Feb 27, 2026) shows illustrative per-sf amounts in worked examples — e.g., a medium MHA area at ~$20.00/sf and a high MHA area (LR3 (M2)) at ~$37.96/sf — but the binding current per-sf table is "Exhibit E" attached to the Tip and is keyed to specific zones; I did not extract a clean verbatim current table, so MHA is reported as a caveat rather than a fee row. WHAT A RESIDENTIAL BUILDER ACTUALLY PAYS (verified, current): 1) Seattle Public Utilities System Development Charges (SDCs), the official adopted schedule effective 1/1/2026. These replace the prior water-only SDC. For a standard residential 3/4-inch meter: Water SDC $6,900 + new Wastewater SDC $2,600 = $9,500. These are additive (both apply to a new single-family connection). Larger meter sizes scale up (1-inch = $11,730 water + $4,420 wastewater, etc.) and are included as excludeFromTotal rows. Wastewater and Drainage SDCs are ONLY charged inside the City of Seattle. Credit is given for existing water/wastewater service or hard surface; wastewater SDC is not charged for irrigation/fire-only services. 2) Drainage SDC: $1,225 per 1,000 sq ft of NEW hard surface (new in 2026, Seattle-only). Charged on increase in hard surface; included as a per_1000_sqft row (not in the per-unit total since it depends on impervious area). 3) King County Wastewater Treatment Division Capacity Charge — a SEPARATE regional charge levied by King County (not the City). Seattle's sewage is treated by King County's regional system, so new connections inside Seattle pay it. 2026 rate = $77.99 per Residential Customer Equivalent (RCE) per month, billed quarterly over 15 years (a medium single-family home = 1.0 RCE = $77.99/mo). A discounted lump-sum payoff is available but King County does not publish the figure (must contact King County). Reported as a monthly per-RCE charge in notes; the 15-year obligation makes the effective lump-sum cost roughly ~$10,000-$13,000 per SFH but the exact lump sum is not published, so confidence on a single dollar figure is lower. CAVEATS: SPU SDC amounts are the 1/1/2026 schedule (current). Water service invoices issued on/before 12/31/2025 used the old water-only SDC. MHA per-sf amounts shown are illustrative example figures from Tip #257, not the binding current Exhibit E table. King County capacity-charge lump-sum total is not published.
Primary per-dwelling-unit residential figures use the standard 3/4-inch (0.75") water meter, which is typical for single-family. Total of additive per-unit connection fees for a new single-family home inside Seattle = Water SDC $6,900 + Wastewater SDC $2,600 = $9,500 (plus drainage SDC based on hard surface, plus the separate King County capacity charge billed over 15 years). Multifamily per-unit SDCs are not published as a flat per-unit number — SPU SDCs are charged by meter size for the building's service, not per dwelling unit, so multifamily is not separately broken out. ADU: not separately published; an ADU added on an existing serviced lot typically receives credit for existing service.
Sources
7 official sources · 5 high-confidence figures.
- 1Seattle Public Utilities - System Development Charge (SDC), Revised SDC (1/1/2026)Seattle Public Utilities (City of Seattle) · fee schedule · effective Jan 1, 2026 · retrieved Jun 16, 2026
- 2System Development Charge and Participatory Latecomer Agreement ProgramSeattle Public Utilities (City of Seattle) · municipal webpage · effective Jan 1, 2026 · retrieved Jun 16, 2026
- 3About the capacity charge - King County Wastewater Treatment DivisionKing County Department of Natural Resources and Parks (DNRP) · municipal webpage · effective Jan 1, 2026 · retrieved Jun 16, 2026
- 42026 Sewage Treatment Capacity Charge BrochureKing County Wastewater Treatment Division · fee schedule · effective Jan 1, 2026 · retrieved Jun 16, 2026
- 5Impact Fees (MRSC) — overview of WA impact fee authority and which jurisdictions impose themMunicipal Research and Services Center of Washington (MRSC) · government report · retrieved Jun 16, 2026
- 6Impact Fees - Office of Planning and Community DevelopmentCity of Seattle Office of Planning and Community Development (OPCD) · municipal webpage · retrieved Jun 16, 2026
- 7SDCI Tip #257 — Developer Contributions: Mandatory Housing Affordability (updated Feb 27, 2026)Seattle Department of Construction and Inspections (SDCI) · municipal webpage · effective Feb 27, 2026 · retrieved Jun 16, 2026
Seattle impact fees — FAQ
- How much are development impact fees in Seattle, WA for a single-family home?
- As of 2026-06-16, total development fees for a single-family detached home in Seattle are about $9,500 per unit — roughly $0 in impact/development fees plus $9,500 in water/sewer connection fees. Figures are normalized from official sources; verify with the jurisdiction before relying on them.
- Are impact fees in Seattle the same as building permit fees?
- No. Impact fees (and water/sewer connection fees) fund off-site capital — roads, parks, schools, utilities — and are charged per new dwelling unit. Building permit and plan-review fees are separate and are not included here.
- How often do Seattle's impact fees change?
- Most jurisdictions adopt fees by ordinance and escalate them annually (often by a construction cost index), with occasional mid-year updates. Always confirm the current adopted schedule with the jurisdiction. ImpactFeeAtlas last verified Seattle on 2026-06-16.